Heterogeneous RNA (H-RNA) is transcribed from DNA sequences reiterated from one to thousands of times. These sequences are used for translation and other unknown functions. The objective of the proposed studies is to determine at what point in the process of transcription, nuclear-to-cytoplasmic transport, and translation a qualitative differences emerges between the H-RNA sequences of normal and malignant cells and to assess its relevance to malignant transformation. In preliminary studies nuclear and microsomal RNA from normal liver were compared by DNA-RNA hybridization with that from 9618A, 7800, and 5123C hepatomas and with livers of animals treated with diethyl nitrosamine. The results suggested that with regard to sequences transcribed from the highly reiterated part of the genome, the earliest changes essential for malignancy involve alteration beyond the level of transcription. In the proposed studies two slow growing hepatomas with normal karyotype and chromosomal number, hyperplastic (preneoplastic) liver nodules, nonneoplastic but rapidly dividing neonatal liver cells and regeneration adult liver cells and normal liver will be fractionated into nuclei, microsomes or free and bound polysomes, and a post microsomal particulate fraction (informosomes). For measuring RNA transcribed from unique or intermediate frequency DNA sequences ribosomal RNA will be removed from RNA preparations thus enabling H-RNA's concentration to be increased 10 to 100 fold. DNA-RNA annealing will be performed using the appropriate DNA sequence, the lowest concentration of purified labeled H-RNA resulting in complete saturation of DNA cistrons, and concentration multiples of unlabeled competitor RNA. The RNA from tumor and normal tissue fractions will be compared and the differences observed compared with those detected between normal liver and neonatal or regenerating liver to determine if they are unique for malignancy or related to normal development or rapid cellular division. Since the presence of polyadenylic acid sequences appears to be required for the transport of some H-RNA sequences into cytoplasm the above results may be extended by using RNA samples enriched for these sequences and determining to what extent differences between the various tissues involve them primarily.